The present invention relates generally to a device for use with a portable inertial navigation system (xe2x80x9cPINSxe2x80x9d) and methods for transitioning between location technologies.
A traditional inertial navigation system (xe2x80x9cINSxe2x80x9d) utilizes accelerometers, gyroscopes, and support electronics, such as a processor, in order to translate sensor data into motional changes. These changes are then translated to a position based on an initial referenced position and the integration or differentiation of the motion. As time progresses, the errors associated with the accelerometers and gyroscopes increase to a point where the translation to a position is outside of the required positional resolution, thus rendering the INS device ineffective or lost.
In one INS embodiment, the INS device is updated manually by resetting the INS device using a known fixed position or by returning back to the original reference position. The user manually resets the INS device and positional errors are cleared until the error occurs again requiring another reset.
In another embodiment, the INS device is updating an alternate location-finding device, such as a global positioning system (xe2x80x9cGPSxe2x80x9d). In this configuration, the attached GPS is providing data to a communication link sending back latitude and longitude information. The INS device is utilized when the GPS position is no longer available due to occulting of the satellites. The INS device is utilized to provide updates to the last known position and errors are accumulated at a rate of 2% to 5% of the distance traveled. The INS device is only used for updating the embedded GPS unit""s location. Once a GPS signal is re-captured, the INS device is not used.
Traditionally, INS devices utilize output voltages representing the second derivative of a position to integrate and determine relative changes in motion. These are applied to the last known position update and a new one is generated with some small error. As time progresses, the errors are accumulated and the computed position is no longer usable by the INS user. A known location or position is required in order to correct for the errors. Traditional systems utilize GPS, or cycle through a fixed reference point to correct those errors.
Thus, there exists a need for a system that reduces error accumulation and performs stand-alone tracking in areas where GPS (or other similar location technologies) can no longer provide location updates to the user or infrastructure.